This invention relates to a safety valve arrangement.
Hydraulically or pneumatically operated machines may be powered via long lengths of flexible high pressure air or hydraulic hose. Flexible hose is used most often in cases where the machinery being operated is portable, such as a pneumatic drill.
Should the hose be severed, or burst loose from its connection on the machine, it may flail around wildly and in an extremely dangerous manner, energised by the high pressure air or water which is still flowing through it. In the past, serious injuries and even deaths have occurred as a result of a person being struck by such a length of hose.
UK Patent No. 2162979 (Edbro) is directed towards the avoidance of the uncontrolled fluid in the event of a rupture in the flow line. A downstream reduction in flow is sensed by means of an electro-hydraulic sensor. Electric power is used to shut off the hydraulic line. External power is thus required to power the sensor and to shut off the main shut-off valve.
European Patent No. 0039643 (Messier) discloses a valve for cutting off the fluid supply in the event of a sudden loss of downstream pressure in the hydraulic system of an aircraft. No downstream sensor is disclosed, and the operation of the valve relies on the relative tensions in a pair of springs which act in opposite directions.
It is an object of this invention to render a high pressure hose harmless in the event of it being severed, by providing a safety valve arrangement for shutting off the fluid supply thereto.
It is a further object of the invention to provide a safety valve arrangement which is sensitive to a downstream loss in pressure, yet which is also relatively rugged, and which does not require any external source of power for its operation.